1. Field of the Invention
The present invention relates to a liquid electrophotographic transferring apparatus for transferring a toner image, formed on an image carrier by using a liquid developer, to a transferring material.
2. Background Information
Hitherto, there have been apparatuses for developing a latent image on a photoconductive body using a liquid developer and transferring the thus developed image onto a transferring material such as transferring paper.
A known apparatus of the type described above is arranged in such a manner that an electrostatic latent image on a photoconductive body is developed using a liquid developer and then the developed image on the photoconductive body and a transferring material overlap each other when a sufficient quantity of carrier liquid is present so as to transfer the image onto the transferring material by means of a corona transference or a bias-roller transference.
However, the apparatus of the type described above sometimes encounters a problem in terms of disorder of the transferred image due to the fluidization of the carrier liquid existing between the transferring material and the photoconductive body at the time of the image transference.
Another apparatus is known which is arranged to perform image transference by bringing the developed photoconductive body and the transferring material into hermetic contact with each other by a roller. However, the apparatus of the above-described type has a problem in that the image on the photoconductive body becomes disordered or the transferred image flows since the carrier liquid on the photoconductive body is fluidized at the time of the above-described contact.
A means for overcoming the above-described problems has been disclosed in Japanese Patent Publication No. 46-1799. The apparatus is arranged in such a manner that two transferring rollers are provided and the first roller has reversed bias when compared to the second roller. With an apparatus of this type, the disorder of the transferred image is prevented to a certain degree but the degree of prevention is not satisfactory.
Another apparatus has been disclosed in Japanese Patent Publication No. 51-44654 in which the image transference is performed after the thickness of the carrier liquid on the photoconductive body has been controlled from 5 to 30 .mu.m by means of a corona discharge of the developer. With an apparatus of this type, the above-described problems is overcome, the transference efficiency is improved. In addition, the unnecessary penetration of the liquid into the transferring material is prevented by making the carrier liquid of a sufficient quantity to perform the wet transference present between the photoconductive body and the transferring material.
According to the method described above, the flow of the transferred image due to the excess quantity of carrier liquid present at the time of the transference is prevented to a certain degree due to the above-described liquid thickness control. However, it involves a problems in that the image on the photoconductive body is disordered due to a corona discharge conducted for the purpose of controlling the liquid thickness. An apparatus has been disclosed in Japanese Patent Laid-Open no. 55-95971 in which a resin solution is interposed between the photoconductive body and a transferring sheet so that the transference quantity is uniform. However, the image disorder that takes place at the time of the image transference cannot be prevented sufficiently.
The applicant of the present invention has disclosed a method in Japanese Patent Application No. 63-052937 based upon a fact that the quality of the transferred image can be improved by arranging the quantity of the carrier liquid to be from 2 to 20 mg per 1 mg of toner after toner development. However, the above-described method encounters a difficulty to control the weight of the carrier liquid and suffers from unsatisfactory quality of the transferred image.
The quality of the image obtained by a so-called commercial printing is higher than that obtained by copying machines which usually employ an electrophotographic method. For example, the 1% half tone of 200 LPI (Line Pair per Inch) corresponds to a diameter of about 16 .mu.m and a resolving power of 35 lp/mm or more is necessary.
According to Japanese Patent Laid-Open No. 61-180248, the liquid electrophotographic apparatuses usually use tone of relatively smaller particle size (1 .mu.m or less) in comparison to dry-type electrophotographic apparatuses.
However, the resolving power excessively deteriorates when the image is transferred to the transferring material. Therefore, the quality corresponding to the above-described printing level cannot be obtained.